Automated multichannel pipette systems used in laboratory research, especially in the biotechnology and medical fields, for simultaneously transferring a plurality of liquid samples between welled trays are known. Such systems include pipettors having a plurality of pumping devices such as syringes which comprise channels having a like number of pistons or plungers disposed therein. The pistons are connected to a moving plate to permit simultaneous movement of the pistons. A removable pipette tip is provided at the lower end of each channel.
Multichannel pipettors are commercially available that can simultaneously dispense samples or reagents into welled plates, typically 96 or 384 wells at a time from a corresponding number of channels or syringes. The welled plates have a standard size of about 3.4 inches by about 5.0 inches regardless of the number of wells and only the spacing between wells and the thickness of the walls between adjacent wells varies. For a 96 well plate, the wells are arranged in an 8.times.12 array with a 9 mm centerline spacing between adjacent wells. A 384 well plate has an 16.times.24 array of wells with a 4.5 mm centerline spacing. Well assay plates having 1,536 wells in an 32.times.48 array and a 2.25 mm spacing are also currently available and plates having wells spaced less than 2.25 mm apart will likely be required for future markets.
Conventional technology requires processing media to be determined and matching liquid handling equipment to be purchased. For example, if a 96 well sample plate is selected for a certain laboratory application, a 96 channel pipettor is required. On the other hand, if a 384 well sample plate is selected, a 384 channel pipettor is required. Multichannel pipettors are expensive and the requirement to specifically match a pipettor to a well plate is impractical in a constantly changing laboratory environment.
A multichannel pipettor can be used to accommodate a smaller number of test wells by mounting a fewer number of pipette tips on the pipettor. For example, a 384 channel pipettor can be used with a 96 well test plate if only one pipette tip is used for every four channels axisymmetrically. However, a standard single well of a 96 well test plate can accommodate a volume approximately four times that of a standard single well of a 384 well test plate. The dynamic volume range of each channel would require very long channels since the volume per stroke length is small due to the 4.5 mm centerline spacing requirement.
It is an object of the present invention, therefore, to provide a multichannel pipetting system and pipette tips that would allow a single multichannel pipettor to be used with different well plates without the inconveniences discussed above.